1. Technical Field
The present invention relates to a display device.
2. Related Art
A display device including an imaging element that forms an image of a projected object and generates a real image in the air using the imaging element has been disclosed in Patent Document 1 (International Publication No. 2007/116639).
The imaging element used for the display device disclosed in Patent Document 1 includes unit optical elements each including a dihedral corner reflector having two orthogonal mirror surfaces. The imaging element has a function of generating a real image of a projected object placed in a space at one side of the element surface in a plane-symmetrical location with the element surface in a space at the other side of the element surface. Accordingly, when a solid object is placed in the space at the one side of the element surface, a stereoscopic image is generated in the plane-symmetrical location with the element surface in the space at the other side of the element surface.
If each unit optical element has one mirror surface and the mirror surfaces of the unit optical elements are in parallel to each other, a real image and a virtual image are generated at both sides of the imaging element. Accordingly, even when each unit optical element has two mirror surfaces orthogonal to each other, light reflected only once on one of the mirror surfaces forms a virtual image. Patent Document 1 has disclosed means for avoiding interference between light reflected twice and light reflected once by the unit optical element, i.e., means for avoiding interference between light forming a real image and light forming a virtual image. Patent Document 1 has disclosed that, as the means, by providing the unit optical element around the axis orthogonal to the element surface in an arbitrary rotation direction, imaging by once-reflected light may be avoided.
However, in the imaging element of Patent Document 1, there has been a problem of cost rise in rotation and arrangement of the unit optical elements in an arbitrary direction because the design and the manufacture of the imaging element become extremely complex. Further, even when the unit optical elements are rotated in an arbitrary direction, light reflected only once by the unit optical element and output stochastically inevitably exists. Accordingly, it has been impossible to completely suppress generation of a virtual image.